1. Field of the Invention
The invention relates to a method as well as an apparatus for the drying and fine grinding of coal for the supply of coaldust-firing equipment to a calcination installation consisting of preheating stage, calcination stage and a sintering stage, particularly for the production of cement clinker.
2. The Prior Art
Experiences with, as well as the safety requirements for coal grinding installations, particularly for the production of coaldust for firing purposes, require above all with solid fuels with a relatively high content of volatile constituents, the reliable rendering inert of the entire grinding installations, or at least of the essential installation parts, mill, air separator and filter. Beyond this, the fluctuating moisture-content of the raw coal frequently occurring with peak values, require a high-tempered drying gas.
It was usual previously in many cases in the state of the art to select the placement of a grinding-drying installation for the supply of firing material to a cement installation, especially with very long rotary kilns, in the vicinity of the calcination platform, and to supply the same with hot exhaust air from the clinker-cooler system.
In this connection reference is made for example to the block circuit diagram on page 491 Zement, Kalk, Gips (ZKG), 1956, Vol. No. 11, in which such an installation is shown and described.
The known arrangement and the method practiced therewith are, however, limited in their recognized, uncomplicated adaptability thereby, that the mill-circulating gas is not inert, for which reason for example upon the processing of coal rich in gas, certain risks are not to be excluded. The preparation of such coals, rich in gas, requires, particularly with reference to these risks and in consideration of the current enhanced safety requirements with corresponding legal regulations, --a rendering inert of the grinding installation to as fargoing an extent as possible.
Furthermore, the question of the starting behavior of the entire installation plays a role insofar that from the ignition of the burner to the possibility of the removal of hot milling-gas from the clinker-cooler, a considerable time span passes by, which must be bridged over with the starting supply from a correspondingly large coaldust-supply bunker.